Musar к Шир ха-ширим 3:6

This idea is expressed in the Zohar in Midrash Ne’elam, Parashas Chayyei Sarah (123b-125b). There Rabbi Pinchas teaches that before a righteous person leaves this world a Heaven voice proclaims throughout Gan Eden, “Prepare a place for the righteous So-and-so who is about to arrive, etc.” Then when the soul enters the gates of the Heavenly Jerusalem the great prince Michoel goes to extend to it a greeting of “Peace!” This causes the rest of the ministering angels to wonder and inquire, “Who is this ascending from the desert?” (Shir HaShirim 3:6). By which they mean from the desolate lower world, which is described as a “desert” by comparison with the upper world. The great prince Michael responds, “She is unique, she is my dove, she is my whole one” (Shir HaShirim 6:9). Note that Michoel does not praise the soul for any particular good deed or righteous quality but only for the quality of wholeheartedness, for this includes all praiseworthy qualities and characteristics. And because this soul embraced all fitting and upright characteristics in the wholeheartedness of its conduct, supernal holiness rests upon it continually. When a person toils in Torah or the performance of the mitzvos, for a distance of four cubits all around him he is encompassed by complete sanctity and his reward is very great.